Liquid vaporizer



H. G. DONALD LIQUID VAPORIZER Oct. 25, 1932.

Filed Aug. 6. 1929 Haw/y 6. 0004/0.

INV

ENTOR BY I ATTOR Patented Oct. 25, 1932 UNITED STATES PATENT OFFICE HARRY G. DONALD, OF THE UNITED STATES NAVY I LIQUID VAPORIZEB (GRANTED UNDER THE AUTO! MARCH 3, 1883, AS AMENDED APRIL 30, 1928; 370 0. G. 757) My invention relates to water tube boilers of the design having one or more elevated steam drums and one or more lower or water drums, the elevated and lower drums being interconnected by rows of tubes. The elevated steam drums r 'e normally operated partially filled with water and the points of entry of the tubes into the elevated drums is below the normal water level in these drums.

My invention resides in the method of and apparatus for reducing turbulence at the liberating surface of the liquid in a steam drum.

The tubes in boilers of the above type are arranged in banked rows parallel to the axis of the furnace, the tubes in each row being staggered with respect to the tubes in the preceding row. It is well known that in all accepted designs of boilers of this type, the location of the furnace and the path of the gases of combustion are necessarily such that the row of tubes adjacent to the furnace receives more heat than the row behind it, and so on through the tube bank, each row receiving less heat. The tubes in the rows which can be seen from the furnace, because of the staggered arrangement of tubes, this number of rows being substantially limited to two, receive heat radiantly as well as by convection through contact with the gases of combustion. It is also well known that these radiantly heated tubes, because of the "higher temperature of the gases next the furnace space, recelve more heat through con vection than do tubes in the rows located at a more distant point from the furnace. It is also true that, as the gas path is followed, the rows more distant each in turn are subjected to lower temperatures of gases. In addition, it is well known that the rows mentioned above receiving heat radiantly, absorb through this means a relatively Very large quantity of the heat liberated in the process of the combustion, this being due to the well known and very much greater rate of absorption of heat through radiant-means as compared to the process of receiving heat by convection.

It will therefore be seen that the hea normally absorbed by a unit area of heating surface in the rows of tubes in a bank of tubes in a boiler of the above described type, is as follows: A very high proportionate amount in the first two rows adjacent to the furnace, considerably less absorption in the first row away from the furnace that receives heat by convection only, and each succeeding row further removed receiving still less.

The effect of the above described condition is a relatively heavy formation of steam in the rows of tubes receiving heat radiantly as well as by convection and considerably less formation of steam in the row next removed which receives practically no radiant heat, and each succeeding row further removed forming less and less steam, and certain rows of tubes farthest removed from the furnace actually serving as down flow for water from the elevated drum or drums to the lower drum or drums. As the mechanical means for insertion of the rows of tubes in the steam or elevatod drum carries the rows across the diameter of the elevated drum there is a heavy discharge of steam through one pointof the water level therein. In A or inverted V types of boilers there are two tube banks disposed on each side of the furnace, the tubes entering the steam drum on an arc to each side of the bottom of the drum, the tubes of the adjacent banks entering the drum radially or at least at some angle so that the projection of the line of entry of the first row of tubes nextthe furnace in each bank meeting on the vertical diameter of the elevated drum well below the normal water level. In other types of stationary boilers there is a tube bank on only one side of the furnace and therefore the rows of tubes adjacent to the furnace is disposed atpne end of the arc of tube entry into the steam or elevated drum. All of these conditions tend therefore to produce an inequality, across the diameter of the steam drum, in the amount of steam which is liberated through the surface of the liquid, there being a tendency toward very great turbulence over a small portion of the liquid level and relative quiescence over a large portion of the liquid level with high velocity of the exit of steam from the liquid surface at the point of great turbulence and low velocity over the area of quiescence. High velocity of steam exit from the liquid surface tends to the entrainment of particles of the liquid. In the generation of vapor from a liquid, entrainment of the liquid with the vapor produced is well known to be objectionable.

It is thus apparent that considering the entire area of the liquid surface in the steam drum, a certain-portion of this area, namely that portion which is substantially over the radiantly heated tubes, is subjected to violent action from the steam which emerges therefrom at high velocity, while'the remaining portion of this area is relatively quiescent.

It is the object of my invention to produce a uniform liberation of steam over the entire area of the liquid surface in the steam drum, the velocity of liberation at no point being sufficiently high to produce objectionable entrainment of the liquid. It is to be particularly noted that this is accomplished by attacking the high velocity currents of rising vapor while they are still submerged, and in no sense is this invention concerned further than the reductlon of entrainment at the point of exit from the liquid level. There are many other means dealing with the removal of entrained liquid from the vapor after its liberation from the body of liquid, but with these I am not concerned, except. that by reduction in entrained moisture I improve the functioning of such apparatus.

I accomplish complete dispersion of streams of vapor approaching the liquid surface at the maximum velocities, and a mingling of the vapor with other similarly submerged vapor approaching the liquid surface at much lower velocity, so as to create the aforesaid equalization of exit velocities, considered across the diameter of the drum.

It is also a feature of my invention that apparatus is not used that will require removal for the ordinary inspection of the tubes or their cleaning.

The above and other objects of my invention will become apparent from the detailed description to follow.

These objects are attained through the construction and arrangement of abafile illus-' trated in its preferred embodiment in the accompanying drawing in which like reference characters indicate corresponding parts throughout the several views, and in which Figure 1 is a perspective view of a dispersing baifie illustrating my invention,

Figure 2 is a cross section of a boiler showing the relative position of the. bafiie in the steam drum thereof, and

Figure 3 is a longitudinal sectional view of the steam drum and bafile.

--Referring more particularly to Figure 2 of the drawing, 5 represents an elevated or steam drum of a water tube boiler, and 6 their way to the li the lower or mud drums, each of the lower I my invention in the drawing in connection with an A type of boiler, it is to be under stood that I do not limit its use to this particular type of boilers as the invention will attain equal efficiency when applied to any othertype of water tube boilers'where the tubes enter the upper drum or drums submerged. Assuming that the furnace, not shown, is situated under and between the two banks of tubes the series of tubes at and Z) are subjected to radiant as well as heat by convection, while the series of tubes 0 and d are not; that is to say, the series a and 6 receive more heat than the series 0 and (Z, that are heated by convection only. Consequently the water in series a and a is heated to a considerably higher temperature and has a higher velocity of entry into the steam drum 5 than the water in series a and 0?. In fact, the outermost rows of tubes in the latter series, they being the most remote from the furnace and receiving but a relatively small percentage of heat, may function as down leads, as

.the tendency of the water therein is to flow downwards instead of upwards. Since the water in series of tubes a and b has a flow of higher velocity than the water in the remaining tubes, greater turbulence of the liquid in the steam drum is produced adjacent to the entry of those tubes than is produced at the entry of the other tubes by the streams emitting therefrom.

The streams of higher velocity of flow from the tubes are dispersed in the liquid in the steam drum by a battle 8 supported in the drum by members 11. It is desirable to construct the battle of such length and width as to cover the projected area of those tubes from which streams of high velocity are ejected. The bafile is preferably V-shape, with the angle between the wings such that the impinging streams will be deflected towards the wall of the drum to mingle with the more slowly moving streams. Without the bafile, the streams from the tubes would be ejected with full velocity toward a vertical axial plane of the drum, there to meet ,or collide and by collision materially add to the turbulence that would be produced by the high velocity alone. As an additional means of minimizing turbulence, the baflle is provided with perforations or openings throughout its area, some of which are shown in Figure 1, through which a portion of the streams may esca e to more slowly make herating surface 10 of the liquid of the drum. As will be particularly noted in Figure 2, the baflle is mounted considerably below the liberating surface 10.

The decrease in turbulence lessens the space required above the level of the water in the steam drum for unevaporated particles to lose their momentum and drop back into the water, thereby making it possible to carry water at a higher level than is practicable in a drum in which there is excess turbulence. My invention further renders it possible to utilize poorer feed water.

It will thus be seen that by the use of a perforated V-shaped baflie wholly submerged below the liberating surface of the liquid in a steam drum and extending over the points of entry into the drum of high velocity streams, but no further, a substantially uniform condition of liberation exists over the entire liberating surface. This equalization is accomplished by dispersing the high velocity currents below the surface of the liquid in the drum'so that they will mingle with the less high velocity currents without producing objectionable turbulence.

The invention described herein may be manufactured and used by or for the Gov- 'ernment of the United States for governmental purposes without the payment to me of any royalty thereon.

It will be understood that the above description and accompanying drawing comprehend only the general and preferred embodiment of my invention and that minor changes in details ofconstruction, proportion and arrangement of parts may be made within the scope of the appended claims and without sacrificing any of the advantages of my invention.

Having described my invention, I claim as 118W:

1. In a liquid vaporizer, a vapor liberating drum having liquid therein, radiantly heated tubes and tubes heated by convection only entering said drum, a perforate bafiie below 40 the normal liquid leveland overlying the inlets of the radiantly heated tubes only.

2. In a liquid vaporizer, a vapor liberating drum having liquid therein, radiantly heated tubes and tubes heated by convection only 5 entering said drum, and a V-shaped baflie below the normal liquid level and overlying the inlets of the radiantly heated tubes only.

3. In a liquid vaporizer, a vapor liberating drum having liquid therein, radiantly heated tubes and tubes heated by convection only entering said drum, and a perforated V-shaped baffle below the normal liquid level and overlying the inlets'of the radiantly heated tubes only.

4. The method of decreasing moisture en-' trainment in vapor liberated at the surface of a fluid, which includes the step of impeding the velocity of the rising vapor bubbles before reaching the liquid surface and producing a substantially uniform distribution of the bubbles over the liquid surface.

HARRY G. DONALD. 

